If it were mine and I was going to spend that kinda $ I'd go ahead an putin the DDEC 6V92TA in it and upgrade it from the DDEC II to DDEC IV. (you guys are techies and should have no problems learning and working on the Pro-link type stuff to keep up with it)

Wait - is it even possible to run a DDEC engine without the rest of the computer control stuff?

What are the advantages (and disadvantages?) of going with an engine with the DDEC controls still integrated?

As you both know I have a lot of time in both a 8v71/v730 and a 6v92ta/v730 in a 4106 and in my opinion there is no question that the TA is a dreamy upgrade! Better fuel mileage, more power, sails over the mountain passes. We live at the foot of Bent Mountain with an 8% grade and my father's 4106 goes up it like a car. I go up it like a bus with a 8v71.....crawling. I wish you where here in Virginia now that you have the driving experience, you could take my dad's bus out for a comparison drive. I couldn't imagine you would ever regret the swap, that engine will always be #1 on my wish list.

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L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaItís the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

My bus at higher altitudes runs hotter. I think it is due to the inefficiencies of a non-turbo and my tendency to make black smoke. My father's bus doesn't know the difference between sea level and eight thousand feet. We both have seven core radiators, and additional Hayden transmission coolers in series with the oil/water cooler. I don't see that many modifications with the swap. My father's bus has an extended shroud or tube that extends out to the fan. It is a simple setup that works. I can get plenty of pics if you decide to pursue it.

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L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaItís the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

Yep they will but the bell housing from your 8v71 is not the same as as 6v92 fwiw and the flywheel is different also kinda of a catch 22 I don't know of a highway coach GM ever made that had a 6V92 the engine it will probably be from a RTS model or other brands and watch those some are right handed not lefties

Regarding your cautious stance on heat dissipation and it's abilities regarding each potential power choice....What are you currently using for a transmission cooler, and is it adequate in IT'S current configuration...WILL it work in an upgrade turbo choice.You might want to post it here for scrutiny also. (or not) It is quite possible that it contributed to your dilemma.

What are you currently using for a transmission cooler, and is it adequate in IT'S current configuration...WILL it work in an upgrade turbo choice.You might want to post it here for scrutiny also. (or not) It is quite possible that it contributed to your dilemma.

Very good point. Here is what I know about the current setup - the transmission oil flows through a heat exchanger mounted on the back bulkhead, where coolant flows in from a pipe that emerges from near the lower exhaust manifold, and then from the heat exchanger it dumps into the top of the radiator.

I can get a picture of the heat exchanger tomorrow and post it - I have no idea how to judge whether or not it is up to the task.

OK, I'm going to throw out another possibility for you to ponder (or a monkey wrench in the works?):

Do like TomC did and rebuild your 8V71 to 8V71T (turbo) specs, but w/o the turbo for now. Don can give the shop all the necessary part numbers for the piston/liner kits and other necessary goodies. Then when you get into Don's neck of the woods, he can add the turbo and fine tune it for you. How much hp do you want? 350? 375? 400? Any of those numbers are easily produced by an 8V turbo. (Personally, I'd just set it up at 350, plenty of giddy-up-go in the '06, almost smoke-free and good longevity.)

Back when I worked in charters, the company had two MC-9s with 8V71TAs @ 350hp, and several 9s with the 6V92TAC @ 275hp. On the 70+ miles of 4, 5 & 6% grades headed to Reno from Sacramento on I-80, the V8s would always outrun the V6s, but overall running time was only 5 - 15 min different. This over 7300' Donner Summit. Basically a wash, and the fuel mileage difference was insignificant at about 6.5 mpg ea. I preferred the V8s, because they would pull longer in the higher gears before being forced to downshift (HT754 Allisons), especially on the milder grades.

Basically, a turbocharger really makes the two-stroke come alive, especially when you start climbing around Rocky Top, plus it helps keep the gendarmes away due to smoke reduction. Not to mention a lot more fun to drive!

One other thought: This would be a good time to have the radiator looked at by a competent radiator shop as a preventative maintenance measure.

Whatever you decide, there are a lot of us paying close attention and supporting you!

First of all.. thank you ALL for your wonderful advice, feedback and ideas. Keep tossing those wrenches at us, we want to explore all feasible options, and will keep following up on them until we reach a decision point. We feel blessed that we're not on a strict time crunch, and have the time to logically sort this out first.

Secondly, just remembered that we took some video of our first engine start on the side of the road after the engine cooled down and refilled the coolant with water.

Keep in mind the HP rating of the V730 when pumping up the HP. I don't remember what it is, but I agree that 350hp is a good number for a 4106. Any turbo option is a good one, it just seems like there are a lot of 6v92 setups out there due to the RTS doners. The turbo lets you travel anywhere as if you where at sealevel.

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L. Christley - W3EYE Amateur ExtraBlue Ridge Mountains, S.W. VirginiaItís the education gained, and the ability to apply, and share, what we learn.Have fun, be great, that way you have Great Fun!

I have no idea what motor will be the best for you but I can pass some information about 871 turbo. A friend of mine had some trouble and I went to Arizona to bring his bus back to Colorado. He has an Eagle and I think his weight is around 38000 LBS. I have driven that road a few times in My Eagle ( 400 horse 4 stroke ). I was surprised how well Don's 871 turbo handled the hills. There was not much difference in the way his bus handled the hills compared to my bus. The only thing is his 871 would heat up more than my 400. I had to keep one eye on the temp gauge in his bus.